JAVA学习笔记031——一个最简单的使用MVC模型实例（登录校验）

目标简述：用户在login.jsp页面输入用户名和密码，LoginServlet拿到数据后，调用LoginDao去和数据库中的数据进行校验，LoginServlet再根据LoginDao的返回结果，决定下一步是重新登录还是进入欢迎界面(Welcome.jsp).

原理图：

5个文件：

JSP: login.jsp 和welcome.jsp

Entity:login.java

Servlet:LoginServlet.java

Dao:LoginDao.java

1.login.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录界面</title>
</head>
<body>
	<form action="LoginServlet" method="get">
		用户名：<input type="text" name="uname"> <br/>
		密码：<input type ="password" name="upwd"><br/>
		<input type="submit" value="登录"><br/>
	</form>
</body>
</html>

2.welcome.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录成功欢迎页！</title>
</head>
<body>
	登录成功！
</body>
</html>

3.Login.java //用户封装数据的javabean

package org.prolific.entity;

//Javabean 封装数据的模型-实体类
public class Login {
	private int id;
	private String uname;
	private String upwd;

	
	public Login() {
		
	}

		
	public Login(String uname, String upwd) {
		this.uname = uname;
		this.upwd = upwd;
	}
	
	public Login(int id, String uname, String upwd) {
		this.id = id;
		this.uname = uname;
		this.upwd = upwd;
	}
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public String getUname() {
		return uname;
	}
	public void setUname(String uname) {
		this.uname = uname;
	}
	public String getUpwd() {
		return upwd;
	}
	public void setUpwd(String upwd) {
		this.upwd = upwd;
	}
	
}

4.LoginServlet.java

package org.prolific.servlet;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.prolific.dao.LoginDao;
import org.prolific.entity.Login;
//控制层（Controller)：接受view请求，并分发给Model处理
public class LoginServlet extends HttpServlet {
    public LoginServlet() {
    }

	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//处理登录
		request.setCharacterEncoding("utf-8");
		String name= request.getParameter("uname");
		String pwd= request.getParameter("upwd");
		Login login=new Login(name,pwd);  //用户名密码
		
		
		//调用模型层的 登录功能
		int result =LoginDao.login(login);
		if (result>0) { //登录成功
			response.sendRedirect("welcome.jsp");
		}else if(result==0) { //用户名密码有误 （重新登录）
			response.sendRedirect("login.jsp");
			System.out.println("用户名密码有误！");
		}else { //系统异常 （重新登录）
			response.sendRedirect("login.jsp");
			System.out.println("系统异常！");
		}
	}
	protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		System.out.println("系统异常！");
	}

}

5.LoginDao.java //用户封装逻辑的javabean

package org.prolific.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import org.prolific.entity.*;

//模型层：用于处理登录（查询数据库）
public class LoginDao{
		public static int login(Login login) {//登录
			int result=-1;
			Connection connection=null;
			PreparedStatement pstmt =null;
			ResultSet rs=null;
			try {
				Class.forName("com.mysql.cj.jdbc.Driver");
				connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/lds?serverTimezone=UTC","root","prolific");
				String sql="select count(*) from login where uname=? and upwd=?";
				pstmt = connection.prepareStatement(sql);
				pstmt.setString(1,login.getUname());
				pstmt.setString(2,login.getUpwd());
				rs= pstmt.executeQuery();
				if(rs.next()) {
					result=rs.getInt(1);
				}
				if (result>0) {  //登录成功
					return 1;
				}else {            //登录失败（用户名密码有误）
					return 0;
				}
				
			}catch(ClassNotFoundException e) {   //登录失败（系统异常！）
				e.printStackTrace();
				return -1;
			}catch(SQLException e) {
				e.printStackTrace();
				return -1;
			}catch(Exception e) {
				e.printStackTrace();
				return -1;
			}finally {
				try {
					if (rs!=null) rs.close();
					if(pstmt!=null) pstmt.close();
					if (connection!=null) connection.close();
					
				}catch(SQLException e) {
					e.printStackTrace();
				}catch(Exception e) {
					e.printStackTrace();
				}

			}	
			
		}

}

JAVA学习笔记031——一个最简单的使用MVC模型实例（登录校验）

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